1. Field of the Invention
The present invention relates to a sizing lapping apparatus which can perform lapping operations with high precision when, for example, a slider of a floating-type magnetic head used in a magnetic disk unit is produced by lapping.
2. Description of the Related Art
An increase in the recording density of magnetic disks has encouraged the production of smaller and lighter floating-type magnetic head sliders used in magnetic disk units, year after year. At present, thin-film magnetic heads are primarily used. In such thin-film magnetic heads, the magnetic gap portion has a very fine structure, making the precision of lapping operations carried out during the manufacturing process a very important factor in determining the quality of the magnetic heads that have been manufactured.
In manufacturing such magnetic head sliders, a plurality of films are deposited on one piece of wafer by a deposition method, during which required circuits are written by a lithography technique in order to form a plurality of thin-film magnetic heads on the piece of wafer at the same time. Then, the plurality of thin-film magnetic heads are sliced from the piece of wafer, whereby the plurality of thin-film magnetic heads are mass-produced. Accordingly, in this manufacturing method, when the thin-film magnetic heads are not precisely processed when they are sliced from the wafer, magnetic head yield may be considerably reduced.
Hitherto, in the case where thin-film magnetic heads are mass-produced by slicing them from a wafer, the gaps of the magnetic gap portions of the thin-film magnetic heads had been formed by the following method.
As illustrated in FIG. 10, a plurality of thin-film magnetic head devices are formed in rows on a wafer 1, which is sliced in a horizontal direction (in FIG. 10) to obtain a sliced-out bar 2 (shown in FIG. 11). As shown in FIG. 12 (which is an enlarged view of the bar 2), a plurality of thin-film magnetic head devices 5 are formed in a row on the bar 2. Each thin-film magnetic head device 5 shown in FIG. 12 comprises a coil portion 6; and four electrode pads 7 that are arranged at one side of its corresponding coil portion 6. To the electrode pads 7 are connected lead wires extending from the corresponding coil portion 6 and lead wires extending from an internal circuit of the corresponding thin-film magnetic head devices 5.
FIG. 13 illustrates an enlarged view of a thin-film magnetic head device 5 of FIG. 12. In the structure of the thin-film magnetic head, the depth to which the gap of a magnetic gap portion g, formed adjacent to the end portion of the coil portion 6, is formed is very important because it directly determines the performance of the thin-film magnetic head 5. Therefore, the bar 2 is mounted to a sizing lapping apparatus in order to lap the top surface of the bar 2 precisely.
In the case where the thin-film magnetic head is a GMR head using a huge magnetoresistive effect element (GMR element), the depth of the gap portion of a read/write head (for reading and writing magnetic signals), the throat height (equivalent to the length of an end portion of a magnetic pole of the read/write head), and the MR height (equivalent to the depth of the gap portion of the read/write head) all depend upon the precision with which the lapping surface is lapped. In addition, both gap portions need to be lapped together. Therefore, it is necessary to achieve very precise lapping operations.
Conventional sizing lapping apparatuses comprise a lap plate, to which a lapping liquid is supplied. In general, when lapping operations are carried out by conventional sizing lapping apparatuses, the lap plate is rotated while a workpiece is pressed against it. In the case where a member such as that in which a sliced bar 2 having a plurality of thin-film magnetic head devices 5 formed thereon is to be lapped precisely, lapping precision may not be satisfactory. In recent years, there has tended to be a demand for such thin-film magnetic heads, in particular, to be lapped very precisely to an order equal to or less than .+-.0.1 .mu.m.
The plurality of thin-film magnetic head devices 5 are formed on the sliced bar 2 by a deposition method. Although they are arranged very precisely on the wafer 1, they may go out of alignment due to bending or deformation of the bar 2 sliced from the wafer 1. Even in such a case there has been a demand for high-performance sizing lapping apparatuses which can perform lapping operations with high precision.